No!  It's not a charcoal replacement thing like some assume. It's does three things, 1. spread the heat a bit more evenly, 2. puts something between the dripping fat and naked flames, otherwise you get flare ups, 3. gets hot so that the dripping juices can vaporise when they hit it.  Using flame tamer plates, porcelain coated 'v' channels or stainless steel sear plates can have the same results.

Lava rock is porous and has a tendency to absorb fat so flare ups gradually increase over a time.  It's always worth a blast of heat anyway before cooking to get rid of any spiders and bugs and to sterilise the grill. Be aware that lava rock does crumble, so your once full basket of big pieces tends to end up in smaller bits and falls through to the grease pan.